Most internal combustion engines mounted on vehicles has a cycle of an intake stroke, a compression stroke, an explosion stroke, and an exhaust stroke, and in particular, a very small amount of mixed air is leaked through an aperture between a wall of a cylinder and a piston during the compression and explosion strokes.
The phenomenon is called a blow-by phenomenon, and the mixed air is called a blow-by gas.
Theoretically, if the space between the wall of the cylinder and the piston is sealed, the blow-by gas will not generated, but the blow-by phenomenon occurs in all vehicles because it is practically impossible to completely eliminate an aperture between the wall of the cylinder and the piston.
Most of the components of the blow-by gas is unburned fuels (HC), and the remaining components are burned gases, partially oxidized mixed gases, and a very small amount of engine oil.
Because the blow-by gas significantly contaminates the atmospheric environment, the recent vehicles have been required to recirculate the blow-by gas into the crankcase, and re-burn and discharge the blow-by gas.
Accordingly, the methods of ventilating the interior of a crankcase include positive crankcase ventilation (PCV), and Korean Patent No. 1163786 discloses a method of recirculating and re-burning a blow-by gas by mounting a PCV valve that may control flow rate according to a pressure difference between an intake manifold and a crankcase, in which because the amount of generated blow-by gas increases as the load of an engine rises, an intake system including an air cleaner, an air inflow part, and an intake manifold is contaminated as the blow-by gas flows backwards to a fresh air inflow hose, and the engine deteriorates, sludge is generated, and in severe cases, an engine failure can be generated as the viscosity of the engine oil lowers and smooth lubrication is hampered.
(Patent Document 1) KR 1163786 B1